Single Stair Housing Studies

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Developing a modular prototype for single-stair housing* in the United States

Primary Projects + RUKA Design
While designing Split Switchback Housing, we tested a few variants to see if it could serve as a prototypical solution for Denver. In 2025, we used the National Single Stair Housing Competition as an opportunity to test the approach on three sites with wildly different dimensions and conditions. 

The Denver project had both street & alley access and was large enough to allow for setbacks on all sides. Across the new sites we tested: zero-lot-line conditions, single-sided fire truck access, on-site fire lanes, and alternative unit layouts.


* Currently, most US housing over three stories requires two means of egress. This generates hotel-style housing, where units are entered from long, dark hallways. This model has many problems. Allowing windows only on one wall leads to inefficient unit layouts that are ill-suited for families, difficult to ventilate naturally, and more. The excess circulation—an extra set of stairs and a long hall—requires large rectangular plots of land, which are increasingly rare and costly in urban settings. Because these codes predate the invention of modern technologies like fire sprinklers, many municipalities are revisiting them to encourage the development of infill sites and lower housing costs.




Logic & Constraints




Street Presence

Sun shading balconies in Austin

Corner balconies and fire lane as lawn in Portland

Alternating balconies in SF




Plans






One Stair, Several Ways

An inset stair in Austin



The peekaboo stair abuts balconies in Portland



Stair as succulent lightwell in SF






Rooftop Vibes

Each roof has space for gardening....

shared meals, and....
laundry





Bonus Content





General Stats

  • 6-stories
  • Amenities: Covered Outdoor Cafe Seating, Community Room, Bike Room, Communal Living Room, Shared Laundry, Rooftop Deck, Social Stair


Austin Stats

  • 20 units:
            6 one-beds
            14 two-beds
  • Lot Size: 6,075 sf (0.14 acres)
  • 144 dwelling units per acre 
  • 244 beds per acre


Portland Stats

  • 16 units:
            12 one-beds
            4 two-beds
  • Lot Size: 5,000 sf (0.11 acres)
  • 139 dwelling units per acre 
  • 174 beds per acre


San Francisco Stats

  • 14 units:
            8 one-beds
            6 two-beds
  • Lot Size: 2,750 sf (0.06 acres)
  • 222 dwelling units per acre 
  • 317 beds per acre

Services

  • Architectural Design
  • Zoning Analysis
  • Interior Design


Tags

Attainable, Communal, Housing, Carbon Smart, Prefab, Missing Middle, Point Access Block




Related Work


Split Switchback Housing

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Socially rich, straw-filled single-stair housing
Primary Projects + RUKA Design
Currently, most US housing over three stories requires two means of egress. This generates hotel-style housing, where units are entered from long, dark hallways. This model has many problems. Allowing windows only on one wall leads to inefficient unit layouts that are ill-suited for families, difficult to ventilate naturally, and more. The excess circulation—an extra set of stairs and a long hall—requires large rectangular plots of land, which are increasingly rare and costly in urban settings. Because these codes predate the invention of modern technologies like fire sprinklers, many municipalities are revisiting them to encourage the development of infill sites and lower housing costs.

Split Switchback Housing answers Denver’s call to imagine American single-stair housing. After completing this project, we tested the prototype at three additional sites with varying constraints. (See Single Stair Housing Studies.)




The first floor caters to residents’ daily needs with spaces for chance meetings, play dates, package deliveries, bike parking, recycling, composting, & trash disposal.







Widespread Adoption

In surveying emerging single-stair legislation across the country, firefighters’ concerns have been the biggest barrier to adoption.

Before starting we worked to understand these concerns better, using them as the foundation to our approach. Building off of Seattle’s code, the design addresses these concerns in the following ways:

(Denver’s Capitol Hill, Station 8, has a truck with a 105’ rear-mount ladder. Denver has adequate hydrant capacity and quick fire department response times. The proposed building has fire sprinklers and properly fire-separated occupancies. All of these are essential factors for taller single-stair buildings.)

Short Travel Distances

The furthest unit is 12’ from the stair. (Also, the stair’s travel distance is equivalent to a typical switchback: 8’ across the landing.)


Fire-Rescue Balconies

Every unit has a balcony facing a right-of-way, allowing for easier rescue and refuge from smoke.


Smoke-Free Stair

The stair is covered, but open at the sides, preventing smoke build-up (and allowing more light & fresh air).


Increased Visibility

The alternating switchback increases visibility between floors (because they aren’t blocked by the level above).












The project consists of two living blocks organized around a central stair. Conceived as a prototypical solution, the blocks can grow or shrink to fit deeper or shallower sites, as long as their inner face abuts the stair.



Click through the gallery below to learn more about the project ︎︎︎




Sponsor

Buildner and ArchDaily

Location

1338 Emerson St / Denver, CO 80218

Awards

BSA / AIA 2025 Unbuilt Planning and Design Merit Award
Denver Single-Stair Housing Challenge, Shortlisted

Stats

  • 6-stories
  • 16 units:
        12 studios
        4 three-beds
  • Lot Size: 5,678 sf (0.13 acres)
  • 123 dwelling units per acre
  • 185 beds per acre
  • Amenities: Covered Outdoor Cafe Seating, Community Room, Bike Room, Communal Living Room, Shared Laundry, Rooftop Deck, Social Stair


Services

  • Architectural Design
  • Zoning Analysis
  • Interior Design


Tags

Attainable, Communal, Housing, Carbon Smart, Prefab, Missing Middle, Point Access Block




Related Work


Communal Housing Design Guidelines

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A book with 40 actionable lessons for designing more communal, affordable, and sustainable multifamily housing
In the face of a housing crisis, a climate emergency, and a loneliness epidemic, how can we create dwellings that foster financial, environmental, and social resilience? Over the last decade, architect Kyle Barker has sought answers to this urgent question. From a master’s thesis on sharing space in the suburban home to founding a mission-driven architecture practice, he has explored diverse housing models such as cohousing, pocket neighborhoods, and cluster apartments. In this book, the outcome of a trip to over 55 housing communities across 10 countries, he distills 40 key lessons for building more communal, affordable, and sustainable housing. Each lesson is illustrated with project photos demonstrating design solutions across the themes of circulation, economy, storage, flexibility, privacy, expression, and economy. This book is for anyone who dreams of better housing!

Purchase your copy here ︎︎︎
If the cost is a hardship, please email us, and we’ll work something out!


Selected Spreads




Timeline

  • Travel: 2022-2023
  • Writing & Editing: 2023-2024
  • Publishing: 2025


Status

Complete

Services

  • Graphic Design
  • Research
  • Writing


Specs

  • 244 pages, plus cover (270+ color photographs)
  • 8” x 10” Soft Bound

Tags

Research, Book, Communal, Housing, Graphic Design

Dodge Mountain House

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A carbon smart house in rural Maine

Primary Projects & Andrew Frederick
Our client­—a young couple with plans for children­—wanted a modestly sized, high-performance, modern house. They purchased a forested plot with distant ocean views and reached out to us with a vision for a multi-volume house inspired by—Croft's founder, frequent collaborator, and good friend—Andrew Frederick’s nearby home.

We aimed to internalize the lessons from Andrew’s house and, if possible, build on them for a family with different needs and site constraints.

The design features two gabled wings set perpendicular to each other: one houses the primary bedroom and bath, and the other contains the first-floor living spaces and the children’s bedrooms above. A mudroom stitches them together, providing a transitional space and simplifying construction.



Construction Photos 👷📸

Click or tap to advance







The L-shaped house is entered at the outer elbow, the junction between the wings







The entry porch takes advantage of the morning sun






Floor Plans

First floor, from top left to bottom right:
  • Primary bed & bath
  • Mudroom / entry
  • Family & guest bath
  • Under-stair laundry & utility
  • Pantry
  • Kitchen
  • Living Space
The upstairs houses two additional bedrooms and a storage loft above the primary bath




The house form creates a protected courtyard, which faces the distant ocean views





The kitchen & living space is connected to the inner courtyard through generous windows & a large door





A window at the sink increases counter space, brings in light, and is a killer spot for bird-watching





The ceiling height - driven by the upstairs bedrooms - makes the modest living room feel spacious






The hall (left) creates a distinction between the social and private spaces of the house while doubling as an excellent art gallery





A window / door pair on the inner courtyard side of the primary bedroom makes it feel like you’re sleeping outside





A view from the storage loft to the primary bed





The entry hall to the primary bed provides the homeowner with an additional layer of privacy





The cedar decking changes orientation as it wraps around the elbow. We get excited about simple moves that feel special without adding cost





Although the house only has a few openings, they are often located across from one another - like the kitchen, shown here - to give the space an airy feel




Locating windows at the corners simplifies prefab panelization and encourages light to bounce as it enters the home 




Client

Private

Status

Under Construction

Location

Rockland, Maine

Services

  • Architectural Design
  • Furniture Selection
  • Interior Design


Credits

  • Andrew Frederick,
    Collaborator


Tags

House, Carbon Smart, Prefab




Related Work


Courtyard Rowhomes

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Affordable missing middle housing for the city
Compact in size and high in quality. The Courtyard Rowhomes are carbon-banking, energy-conserving, community-supporting, adaptable houses that allow for as many living arrangements as their residents can imagine.

Two rows of five homes orient toward a shared courtyard. The courtyard is broken into several bands that facilitate circulation, social connection, and privacy. The central band allows feet and wheels to move freely. It's bracketed by each unit's dedicated outdoor space. These patios activate the courtyard and create a series of resident-defined possibilities: shared meals, playtime, group fitness, and more. Planters between the buildings and the patios keep neighbors at a comfortable distance and screen views.




Ground Floor Plan. Ten rowhomes on two single-family lots: five on the street side and five at the rear


Second Floor Plan



All of the units can be entered from the central courtyard. Kitchens face this space to foster social connection and buffer more private spaces






Resiliency & Sustainability

Every day, we wake up to troubling headlines about climate change. Unfortunately, many high-performance buildings rely on high-embodied carbon materials like foam insulation to achieve operational energy savings. What if we could replace those materials with ones that perform well, draw in and store carbon, naturally regenerate, and grow nearby?

The Courtyard Rowhomes are made from straw-filled prefabricated panels manufactured in a shop and brought to the site. Each panel has two rows of 2”x4” studs (a “double stud” wall), is filled with 12” of straw, and is wrapped with sheathing and weather control layers.
Other sustainability features include:
  • Concrete is reduced to a grade beam infilled by an insulated double-layer plywood “slab,” which significantly reduces carbon emissions
  • Ceiling heights are kept to 8’ to utilize standard lumber and maximize drywall yields
  • Downspouts feed below-grade cisterns to minimize runoff
  • Each room has at least two operable windows for cross-ventilation
  • Plumbing fixtures are near the water heater to lower energy use and
  • Solar panels could be installed on the flat-seam metal roof when the orientation merits it.



Pathway from the street to the courtyard

The siding follows the pitch of the roof



The space beneath the stairs can be used for storage



View through the kitchen to the living space and the rear entry



Universal Design & Aging-In-Place

The Courtyard Rowhomes incorporates Universal Design best practices like:
  • An on-grade entry
  • Zero or minimal thresholds at doors and flooring changes
  • Generous maneuvering clearances and knee space in kitchens and bathrooms
  • Wide doorways and hallways
  • Bathroom grab bars, and
  • Reachable controls throughout
Typically, these accommodations require more square feet (SF), which can be challenging when building footprints need to be smaller. To solve this problem, we worked diligently to overlap maneuvering clearances with circulation pathways.

One example: the 4’ x 4’ maneuvering clearance at the entry coincides with the landing at the bottom of the stairs. This consolidates the clearances, forms a generous entry, and creates a mudroom-like buffer into the main living space. Design moves like this help to create an accessible 867 net SF house that lives much larger than its small footprint would suggest.




The kitchen connects to the courtyard; residents can use their shades to convey how social they’re feeling




Client

Private

Status

On Hold

Location

Brockton, Massachusetts

Services

  • Architectural Design
  • Interior Design
  • Furniture Selection
  • Zoning Analysis


Tags

Affordable, Communal, Housing, Carbon Smart, Prefab, Missing Middle

Stats

  • 2-stories
  • 10 units: 2 or 3 bedrooms (depending on resident)
  • Lot Size: 12,260 sf (0.28 acres)
  • 36 dwelling units per acre
  • 71-107 beds per acre (depending on residents’ configuration)
  • Amenities: Shared Courtyard, Bike Parking





Related Work



Data Port

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How could we reimagine the data center as a civic amenity?
This project reimagines the data center typology to maximize its ability to shed heat. What would typically be expelled as “waste heat” is repurposed to sponsor a range of civic activities & one of a kind experiences. The site—the only break in the Harbor Walk from its start in Charlestown—is transformed into a destination with a global reach, like the data it houses. Visit the desert. Visit the tropics. Soak up the hot springs. Luxuriate in the thermal baths. Jump on the splash pad. Whoosh down the waterslide. Swim like an olympian. Run like a marathoner. Experience a geyser. Learn about data.

All of these experiences are made possible by the heat from the servers, which literally float across the historic dry dock as a single, meandering row. The pools are used as a heat sink, via a closed loop radiant system—“Direct to Chip Cooling” using non-flammable dielectric fluid—whose flexible piping is set into deep grooves in the flooring & walls of the pools; visible to its users, but out of reach. This technique utilizes the heat-carrying capacity of liquid, which is 3,500 times greater than air, to cool the racks. This is the one time in Architecture where a maximal building envelope is the environmentally friendly, cost-effective choice! Although this approach minimizes the waste heat as air, one can never completely eradicate it, so why not utilize it to inflate a one-hundred-foot tall pneumatic greenhouse? The constancy of the waste air, typically a problem, allows for a monumental gesture on the scale of the Seaport. (And because the structure is year-round, even in the hot months, it raises the question, “What happens when you have too much air?” Answer: you power an artificial geyser as an evaporative cooling homage to the whales.)


The data center’s servers float in the former dry dock, releasing waste heat to warm a series of pools and inflate two 100-foot tall pneumatic greenhouses (of course)








The former buoyancy chamber at the center of the dry dock hosts the servers and a series of pools. Greenhouses bracket the pools, and an elevated running track stitches everything together



Soak up the hot springs



Luxuriate in the thermal baths



Jump on the splash pad & whoosh down the waterslide




Swim like an Olympian & experience a geyser 




Visit the Tropics! The continuous waste heat from the servers inflates a pneumatic greenhouse. A running track allows visitors to view the plants from the ground, 40 feet in the air, and everywhere in between




Visit the desert!



A long section through the pools (click it to navigate)





A plan of the pools (click it to navigate)




A view from the museum’s basement through the data center into the swimming pool



Experience the glow of the data




Client

Competition

Timeline

2021

Location

Boston, Massachusetts

Award

2021 Rotch Prize Winner

Services

  • Architectural Design
  • Interior Design
  • Exhibition Design
  • Urban Design


Tags

Civic, Park, Data Center, Dreams




Related Work

Permanent Collection

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An architecture museum that uses itself to teach people about architecture
An architecture museum is one of the few buildings that has to house and display other buildings. From the full-scale prototype to the microfiche archive, the scalar range of the collection is immense. This project harnesses the extreme dimensional difference of the objects in its collection to propose a building with radical shifts in section. As the ceiling height shrinks from 35’-0” to 11’-0” across five floors, the structural systems shifts to accommodate larger spans, more columns, etc. With these changes comes the opportunity to recall five canonical plan organizations: the free plan, the ring (with atrium), the hypostyle hall, the forest, and the villa. As the visitor ascends—either through the glass elevator or the spiral stair—they experience pronounced material, structural and spatial shifts, sampling a history of Architecture on their way.












Level 1 - Infrastructural Clear Span









Level 2 - Castellated Atrium










Level 3 - Waffle Hypostyle 










Level 4 - Column Forest









Level 5 - Mass Timber Renaissance









Roof Top - Field of Figures






Client

Competition

Timeline

2020

Location

Boston, Massachusetts

Award

2020 Rotch Prize, Runner-Up

Services

  • Architectural Design
  • Interior Design
  • Exhibition Design


Tags

Civic, Museum, Dreams




Related Work



Model Homes

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A test bed for new models of communal living
Model Homes is an ongoing project to test ideas that haven’t found a project yet. It’s a way of pushing ourselves to think beyond the known models of collective housing. 

All of these begin with the combination of:
  • a common demographic:
    cohabitating adult friends, two families with young children, intergenerational families, etc,
  • and a simple spatial idea:
    typically something grid-based to simplify construction

When working on them we jump between plan, section, and model. We often work on several at a time, and we’ve found the multiplicity of options within a house and across houses simultaneously to be freeing. It’s helped us to shed preciousness and embrace the aspects of architecture we love: embedding the concept into the core of the architecture (structure, organization, light) and imagining new modes of living.





Grid House ︎︎︎

What happens when you combine cohousing & grids? This house can be used as two standalone homes that share a wall, or as one large, luxurious space for cohabitation. Borrow sugar through the “window” in the kitchen. Dine like Thanksgiving any night of the year. Get that good, good laundry smell every day. Sneak off to your own private living space, or throw a rager in the dining / living area. #NotForSquares










Telescoping House ︎︎︎

Gables on gables on gables, each one housing a different type of space. A house for four+ friends who want to cohabitate and co-locate their businesses. The beds & baths are bracketed by a large living area and a divisible business-from-home space. Launch your plant shop. Run your accounting firm. Curate your vintage shop. The possibilities are endless! #BusinessInTheFront








Tube House ︎︎︎

We always say that the only thing better than skylights is tall skylights. Designed for the needs of a multi-generational family, this house is made up of a series of alternating living & sleeping spaces. Whether it’s the den, patio, reading nook, home office, TV room, or eat-in kitchen, each person can choose the space that suits their mood. #LetTheLightShineIn









Pier House ︎︎︎

Formed from six “service” piers, this two-family co-house uses half-levels to create privacy between the living and private zones. The central living / kitchen / laundry area is the social hub. Moving out from there are each family’s bedrooms and private spaces (shown here as a nursery and a home office). #MeetMeInTheMiddle








Zig Zag House ︎︎︎

In this house for four+ friends, we wanted to test what would happen if we combined two of our favorite things: a sawtooth plan and a gable section. The result is a large central living / kitchen / laundry area, bracketed by private living areas that can be contiguous or not, based on user preference. The bedrooms bookend the building and have access to a shared patio through their private entries. #DiamondsAreForever







Client

Self-Initiated

Timeline

2021

Status

Complete

Services

  • Architectural Design
  • Interior Design
 

Press

One House per Day

Tags

Communal, Housing, Dreams




Related Work

One Plus Two House

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A carbon smart house in rural Maine made of straw
It’s a good fit when a client says any of the following:
  • “We want something really sustainable.”
  • “We don’t want a house that’s too large.”
  • “We want it to sit gently on the land.”
  • “We like modern but cozy.”

In this case, the client said it all on our first call. We told them it felt like, “Dream Client Bingo.”



Surrounded by wood at the entry to the house & screened-in porch.






The family of simple gable forms helps break down the scale of the house and anchor it to the sloped site







Ground Floor Plan
From left:
  • Screened-In Porch
  • Deck
  • Living Room: With dining, kitchen, and large sliding doors to patio
  • Pantry
  • Stair to second floor
  • Laundry & Utility Room
  • Bathroom
  • Guest Bedrooms





The bookcase provides storage for chopped logs as well as: a place to put the TV, additional seating, and a spot for books





The Southeast corner of the house provides expansive views of the pond.





From left: entry, stair to mezzanine, hall to the guest bedrooms, kitchen & pantry.





The house is perched among the trees







Second Floor Plan
From left:
  • Stair to first floor
  • Mezzanine: With banquette seat, storage, & sitting area
  • Primary Bathroom
  • Primary Bedroom: With walk-in closet and private deck





The second floor overlooks the first, but we designed a screened railing, a seating nook, and a storage wall to give it its own character.





The primary bedroom has its own deck with views to the pond





We’re fairly confident there isn’t anything better than a morning coffee with pond views on the terrace outside your bedroom.





Client

Private

Location

Warren, Maine

Services

  • Architectural Design
  • Interior Design


Credits

  • Primary Projects Team,
    Kyle Barker, Jacqueline Traudt
  • Croft,
    Collaborator & Straw Panel Provider

Tags

House, Carbon Smart, Prefab





Related Work

View at Rear Entry

Thick House

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A modular home designed to be built in a controlled environment and assembled on site; a workaround for a remote site without a nearby labor force
The platform frame is primarily about speeding up construction and maximizing interior square footage. Although these are typically marshalled as economic arguments, they are often trotted out as sustainability arguments. We’re using less! We’re being economical!

What these arguments omit is the extraction processes and intense energy use demanded by their manufacture and/or erection. Aluminum and foam, the worst offenders, epitomize this twentieth century mentality about buildings: build them light, fast, and hollow and clad them in something like vinyl that can weather temperature swings and time.

Rather than thinking about wall & floor assemblies as individual components, responsible for singular functions (studs for structure, building wrap for moisture mitigation, insulation for R-value) lets thicken and sculpt our walls so that their inherent geometry buttresses them, their materiality resists moisture, their thickness combats rapid heat transfer, their surface provides a home for piped service runs, and their form affects us!








View of Living Room
View of Living Room









Junction of Four Modules
Junction of Four Modules



View from Rear
View from West





West Elevation




Entry at North
Entry at North




North Elevation




View from Bed




View from Bedroom to Entry
View from Bedroom to Entry





Section, looking South




Ceiling Modules
Roof Modules














View of Kitchen
View of Kitchen




View from Kitchen to Living Room




Junction of Six Modules
Junction of Six Modules



Panning view of the Living Room




Client

Competition

Timeline

2017

Award

2017 Rotch Prize, Finalist

Services

  • Architectural Design
  • Interior Design
  • Furniture Selection  


Tags

Prefab, House, Dreams